 ! function (win) {
     function resize() {
         var domWidth = domEle.getBoundingClientRect().width;
         if (domWidth / v > 750) {
             domWidth = 750 * v;
         }
         win.rem = domWidth / 3.5;

         domEle.style.fontSize = win.rem + "px";
     }
     var v, initial_scale, timeCode, dom = win.document,
         domEle = dom.documentElement,
         viewport = dom.querySelector('meta[name="viewport"]'),
         flexible = dom.querySelector('meta[name="flexible"]');
     if (viewport) {
         //viewport：<meta name="viewport"content="initial-scale=0.5, minimum-scale=0.5, maximum-scale=0.5,user-scalable=no,minimal-ui"/>
         var o = viewport.getAttribute("content").match(/initial\-scale=(["']?)([\d\.]+)\1?/);
         if (o) {
             initial_scale = parseFloat(o[2]);
             v = parseInt(1 / initial_scale);
         }
     } else {
         if (flexible) {
             var o = flexible.getAttribute("content").match(/initial\-dpr=(["']?)([\d\.]+)\1?/);
             if (o) {
                 v = parseFloat(o[2]);
                 initial_scale = parseFloat((1 / v).toFixed(2))
             }
         }
     }
     if (!v && !initial_scale) {
         var n = (win.navigator.appVersion.match(/android/gi), win.navigator.appVersion.match(/iphone/gi));
         v = win.devicePixelRatio;
         v = n ? v >= 3 ? 3 : v >= 2 ? 2 : 1 : 1, initial_scale = 1 / v
     }
     //没有viewport标签的情况下
     if (domEle.setAttribute("data-dpr", v), !viewport) {
         if (viewport = dom.createElement("meta"), viewport.setAttribute("name", "viewport"), viewport.setAttribute("content", "initial-scale=" + initial_scale + ", maximum-scale=" + initial_scale + ", minimum-scale=" + initial_scale + ", user-scalable=no"), domEle.firstElementChild) {
             domEle.firstElementChild.appendChild(viewport)
         } else {
             var m = dom.createElement("div");
             m.appendChild(viewport), dom.write(m.innerHTML)
         }
     }
     win.dpr = v;
     win.addEventListener("resize", function () {
         clearTimeout(timeCode), timeCode = setTimeout(resize, 300)
     }, false);
     win.addEventListener("pageshow", function (b) {
         b.persisted && (clearTimeout(timeCode), timeCode = setTimeout(resize, 300))
     }, false);
     /* 个人觉得没必要完成后就把body的字体设置为12
     "complete" === dom.readyState ? dom.body.style.fontSize = 12 * v + "px" : dom.addEventListener("DOMContentLoaded", function() {
      //dom.body.style.fontSize = 12 * v + "px"
     }, false);
     */
     resize();
 }(window);